This invention relates to abrasive saw blades or cutting wheels for cutting concrete, asphalt and masonry materials. More specifically, the invention relates to an abrasive blade with a plurality of diamond impregnated segments affixed to a circular metal core for cutting stone-type materials.
Industrial saw blades referred to as the discontinuous rim or segmented type blade are well known and currently in widespread use. This type of blade is conventionally made by mounting to a circular core a series of short arcuate abrasive cutting segments containing diamond powder disbursed in a metal matrix. These cutting segments are usually about two inches long and are ordinarily silver soldered, brazed or welded to the rim of a steel core which has been divided into a plurality of support sections having peripheral surfaces for supporting the cutting segments.
The support sections are separated by radially extending gullets which accommodate the large thermal stresses created by the frictional heating of the blade periphery during cutting operations as well as the large thermal stresses created during the mounting of the cutting segments on the blade core during manufacture. Segmented blades have been accepted by those industries that subject the blades to heavy-duty use, such as the concrete, asphalt and masonry cutting industries where rough abrasive cutting is commonplace.
Although segmented blades may be designed for dry cutting, it is more common to continuously flush the cutting area during the cutting operation with a fluid coolant such as water in order to keep the blade as cool as possible. The coolant also serves as a lubricant to flush loose rock-like material, spent abrasive and the like from the cutting site, all of which in combination with the coolant forms an abrasive slurry which is generally referred to in the industry as “swarf”.
Even though construction of segmented blades has been developed to a high degree of reliability, blades must commonly be replaced whenever the swarf erodes the steel drive core adjacent the junction of the cutting segments with the core. This erosion occurs radially inwardly of the cutting segments around the weldment between the segments and the core and is commonly referred to as “undercutting”.
The phenomenon of undercutting is particularly bothersome because it significantly reduces blade life. Even though up to half of the original material of each abrasive cutting segment may remain, the entire blade must be replaced for reasons of safety when severe undercutting is noted. Otherwise, the likelihood increases that one or more segments will break loose during cutting operations when the blade is rotating at a high rate of speed and a potentially dangerous condition results.
In addition to the safety hazard, undercutting has an economic impact as well. Since the abrasive segments are the most costly portion of the blade, significant economic loss is incurred by undercutting due to nonuse or waste of the remaining cutting segment material. In addition, frequent replacement of undercut blades further reduces productivity by increasing the downtime workers spend in replacing the blades instead of operating the saw.
Undercutting of saw blades is particularly acute when “green” concrete is being cut. Green concrete is concrete in its relatively freshly poured state prior to fully curing. Curing can take from 4 to 60 hours to complete. During this time, the green concrete begins to shrink. If this shrinkage is not controlled, cracks will form throughout the concrete. Accordingly, it is common to cut grooves in green concrete for stress relief and crack control. Such grooves are commonly referred to as contraction joints. Because green concrete is not fully hardened and cured, it is particularly susceptible to forming highly abrasive swarf, which aggressively acts to undercut segments of the saw blade.
In the past, numerous solutions have been directed to the problems of undercutting and segment lose. U.S. Pat. No. 4,291,667 of Eichenlaub et al.; U.S. Pat. No. 4,854,295 of Sakarcan; U.S. Pat. No. 5,787,871 of Jones et al.; and U.S. Pat. No. 5,839,423 of Jones et al. each acknowledge such problems and are representative of some of the previously proposed remedies. Generally speaking, past attempts have focused effort on better ways to mount the segments onto the core or to remove or flush the abrasive swarf from the cutting site. Such efforts have achieved only limited success.
Some of the prior attempts to reduce undercutting have included asymmetrical cutting elements or dimensional variances of the gullets between successive segments in an effort to protect the symmetrical or uniform cutting elements or to create a turbulent flow pattern, as opposed to a laminar flow pattern, of the swarf around the blade. Such changes in abrasive blade design have many times resulted in increased blade vibration and wear.
Accordingly, a need exists in the industrial cutting industry for a segmented abrasive blade having improved wear characteristics to prevent premature wear adjacent the bond line formed between the blade core and the cutting segments. The primary object to this invention is to meet this need.